Tuesday is the sixth day of extra security measures at airports

By 1130 BST on Tuesday, eight flights had been cancelled - five from Glasgow Airport to London and Southampton and a further three from Aberdeen Airport.

Edinburgh Airport was "busy" but no delays or cancellations were reported.

The disruption followed tight security after an alleged plot to blow up planes in mid-air was foiled. The threat level to the UK stands at severe.

On Monday, the Home Office downgraded the threat level to the UK from critical.

It said the decision had been made because an attack was "highly likely" but no longer "imminent".

BAA 'incompetent'

The change in the threat level meant the ban on taking hand luggage on to flights from the UK was lifted, although some restrictions remain.

A senior Scottish labour MP has criticised BAA's conduct amid heightened security and in particular the management of Heathrow Airport.

Brian Donohoe, the MP for Central Ayrshire, accused the company of "incompetence ".

Mr Donohoe travelled from Glasgow to Heathrow on a British Airways flight on Monday.

These are extraordinary times and airport staff have been working under extreme pressure BAA spokesman

He said: "It is patently obvious that Heathrow have been unprepared for such events to take place.

"It is clear to the travelling public that they simply don't have the skills to deal with the situation.

"I believe the government, with such draconian measures in place, have a responsibility to press BAA to have the appropriate skills and failure to do so should lead to a government rethink on the use of alternative resources."

A BAA spokesman said the operator understood the frustration of passengers and that it was working extremely hard to resume normal services.

He said: "However, these are extraordinary times and airport staff have been working under extreme pressure.

"Throughout this difficult situation, they have given nothing less than their very best and we are proud of the commitment, professionalism and dedication they have shown.

"It is easy to criticise from the sidelines.

"However, ill judged comments such as these do nothing for the morale of the thousands of airport staff who are working hard to ensure the safety and security of millions of passengers at what is clearly a time of heightened national security."